i recognize him as the boyfriend. >> reporter: bennett picked out stephen cooke. heidi's boyfriend was arrested for first degree murder. >> deep in our hearts, we all had a feeling that he had something to do with it. >> reporter: stephen's trial began in june 2015. he pleaded not guilty. glennon and breault had the task of convincing a jury that stephen was capable of orchestrating a cold murder-for-hire. their case would rely heavily on the word of one man the killer himself, alexander bennett. you really had to believe this guy, bennett? >> absolutely. >> reporter: your case was gonna rise and fall on that? >> he was going to be the star witness against stephen cooke. >> reporter: bennett told jurors the same story he told investigators how he killed heidi. video cameras weren't permitted, but bennett's testimony was audiotaped. he decided to confess he says because of his faith and for heidi's family.